Until recently, human diseases of viral etiology have proved to be very difficult, if not impossible, to treat successfully. Chemical antiviral agents currently comprise the most widely used treatment. Some chemical antiviral agents, however, such as, for example, azidothymidine (AZT), may cause serious and unpleasant side effects which lead to the contraindication of their use in many patients infected with viral diseases. In addition, the high cost typically associated with many of these chemical agents may effectively preclude access to such treatment by many in need. In addition, the chemical antiviral agents are generally not equally effective against a broad spectrum of viruses. Such antiviral agents, therefore, have a more limited usefulness for the general population than may be desired. Consequently, researchers have turned their attention to the development of other methods of achieving antiviral activity to combat diseases of viral etiology that have proved refractory to available therapies.
As the mechanisms of viral infection have become better understood, approaches to combatting human diseases of viral etiology based on these mechanisms have been proposed. For example, Baker in U.S. Pat. No. 3,577,525 suggests a method of inducing resistance to infectious viruses in animals. An essential aspect of Baker's method employs a virus or bacterium alien to the animal to develop complement-fixing antibodies in the animal to the infectious virus. In addition, the alien virus or bacterium must be immunologically unrelated to the infectious virus. Baker's method is disclosed to be an effective method of protecting a horse against infectious equine rhinopneumonitis by the use of bovine rhinotracheitis virus to produce in the horse complement-fixing antibodies against the equine rhinopneumonitis virus. Although this method may effectively induce immunity to viral infections in animals, there is no suggestion that it has any application to the treatment of viral diseases in humans already infected with the virus.
U.S. Pat. No. 4,053,582 to Stickl suggests the attenuation of fowl pox virus to form a new virus no longer pathogenic to fowl which induces the production of interferon. This new virus is suggested to be capable of administration to animals and humans to treat a wide variety of infectious diseases. The level of interferon production achieved by this new virus in animals appears to depend on the route by which the virus is administered. Although this patent suggests the rather widespread application of the attenuated fowl pox virus to infectious disease of both viral and bacterial etiology, the only specific examples presented relate to the treatment of herpes, influenza and viral warts in humans and to the treatment of certain virus-caused animal infections, such as equine influenza and pigsty epidemic. Although the new viral strain disclosed in this patent may treat these conditions effectively, there is no suggestion that its efficacy extends further to encompass other human diseases of viral etiology, such as hepatitis, viral neoplastic disease or acquired immune deficiency syndrome.
Cancer research has for years focused on identifying causative viral agents in the hopes that vaccines specific to these causative agents could be developed. While the successful identification of such specific causative agents has thus far not been fully achieved, researchers have suggested the use of antitumor viral agents to treat various mammalian tumors. For example, Wallack, in U.S. Pat. No. 4,108,983, discloses using the vaccinia virus (the agent used to make currently available smallpox vaccines) to lyse species-specific tumor cells and produce an injectable oncolysate that appears effective in treating some kinds of tumors. However, the production of this antitumor agent is dependent upon obtaining a sample of tumor cells from the specific patient to be treated, either surgically or otherwise, to produce the antitumor oncolysate. Consequently, this method is not likely to have widespread efficacy.
Japanese Publication No. 58-116422 discloses an antitumor agent that contains a live vaccine of attenuated paramyxovirus which exhibits an antitumor effect in mice. The antitumor agent described in this publication is not disclosed to be effective against conditions other than the specific mouse tumors studied.
An additional infectious disease of viral etiology that has increasingly become the focus of public attention in recent years in human acquired immune deficiency syndrome (AIDS). Although chemical antiviral agents such as AZT have been used to treat AIDS with some success, these agents suffer from disadvantages, such as the side effects previously mentioned, as well as their high cost. While much research effort has been directed to identifying treatments effective against AIDS, this effort has focused primarily on the development of potential chemical pharmacological and pharmaceutical agents. It has not been suggested to employ a virus in the treatment of AIDS.
The prior art, therefore, fails to suggest a method for treating human diseases of viral etiology which employs an antiviral agent that is readily available and easily produced and which employs as the specific antiviral agent an attenuated virus and which is effective in treating a wide spectrum of diseases of viral etiology, many of which pose major public health problems.